Neutralizing system and method



April 5, 1949. H. E. WEAVER 2,466,629

NEUTRALIZING SYSTEM AND METHOD Filed Dec. l5, 1945 2 Sheets-Sheet l eAeAAV Y e@ 22d/WW f- Q v 20 ZAZL 25a 2307 "9W l M April 5, 19491 H. E. WEAVER 2,466,629

NEUTRALIZING SYSTEM AND METHOD Filed Dec. l5, 1945 2 Sheets-Sheet 2 Patented Apr. 5, 1949 UNITED STATES PATENT OFFICE NEUTRALIZIN G SYSTEM AND METHOD Holla Edwin Weaver, Maywood, Ill.

Application December 15, 1945, Serial No. 635,377

Claims. 1

This invention relates to neutralizing systems, and has to do with a system for, and method of, neutralizing induction in communication lines paralleling power lines.

It frequently is necessary for communication lines, such as telephone, telegraph, railway signal and other signal lines, not used primarily for transmitting power, to parallel closely alternating current power transmission lines for considerable distances. The inductive effect of the power line on the communication line, at such parallels, causes objectionable interference in the communication line, particularly in the event of an unbalanced load or a fault in the power line.

Numerous attempts have been made to prevent interference in communication lines paralleling power lines, but none of such attempts has to my knowledge provided an entirely satisfactory solution of the problem, nor succeeded in reducing the interference to such an extent as to be unobjectionable and, in present practice, considerable interference in a communication line paralleling a power line is accepted as being unavoidable. It is known to provide at a parallel a shield wire in the communication line, transformer coupled to the signal transmitting wires of that line. In such a system, the shield wire must extend the full length of the parallel and should be of low resistance well grounded, which frequently entails considerable expense and is objectionable for that reason. If there be a number of communication lines in a parallel, each of such lines must be provided with a shield wire, with attendant increased expense. The voltage induced in the shield wire of the communication line, by the power line, can be no more than that induced in the signal transmitting wires of the communication line. The resistance in the shield wire, including the transf-Ormel' and grounds thereof and the resistance of the wire itself, shifts the phase of the current induced in that wire by the power line and energy losses in the transfarmers are inevitable. The result is that the neutralizing voltage induced in the signal transmission wires ci the communication line is less than the interfering voltage induced in such wires by the power line, and is never in completely reverse phase or 186 out of phase with the latter voltage.

It is, therefore, impossible, in the known system referred to, to completely neutralize the voltage induced in the signal transmitting wires of the communication line by the power line. It has been proposed, in su'ch known system, to use condensers and reactances in an endeavor to bring the induced current in the shield wire more nearly into phase with the current induced in the signal transmission wires of the communication line by the power line. That has not been entirely successful, nor does it in any way avoid the basic dilculty referred to, namely, the fact that the voltage induced in the signal transmission wires of the communication line by the transformer coupling thereof to the shield wire is never equal to the voltage induced in such transmission wires by the power line, so that the latter voltage can never be completely neutralized even if the difficulty with respect to phase difference were completely overcome. The use of condensers and reactances does not solve the problem and adds materially to the cost of the system, which is objectionable for obvious reasons.

I have discovered that it is possible to neutralize completely voltage induced in a communication line by a power line, by applying to the communication line neutralizing voltage determined by energy derived directly from the .power line in contraclistinction to energy derived from a shield wire or like source included in the communi-cation line. 'Io that end, I provide in the power line transformer means effective to eval uate the interfering eiect of that line, and introduce into the communication line, under control of such transformer means, voltages of proper phase and magnitude to neutralize the voltages induced in the communication line by the power line. The transformer means of the power line is directly coupled to the means for applying to the communication line neutralizing voltage, which latter may be accomplished by either electronic means or magnetic means, or other suitable equivalent means, though ordinarily I prefer to use magnetic means. In the latter case, the transformer means in the power line is directly coupled to neutralizing transformer means in the communication line. Since the energy derived from the power line, by the transformer means thereof, is much greater than that induced by the power line in the communication line, it is possible not only to neutralize completely the communication line, but to over neutralize it, if desired, which is advantageous in certain cases. It is not necessary in such a system to use an auxiliary wire or grounds, though they may be used if desired. When an auxiliary wire is used, it is included in the power line, with the advantages noted with respect to available neutralizing energy, and may be quite short relative to the parallel, a distinct advantage with respect to parallels of considerable length. If there are several communication lines in a parallel, as frequently occurs, each thereof may be neutralized from the transformer means of the power line, in the manner above stated, avoiding necessity of providing a shield wire for the full length of the parallel in each communication line, as is necessary in the known system above referred to, with a corresponding saving in cost. Also, in cases where a power line and a cornmunication line closely parallel, then separate widely and again parallel, it is possible to neutralize the communication line at both parallels by over neutralizing one of the parallels sufficiently for that purpose, thereby avoiding in many cases duplicate installations of the system of my invention with a corresponding saving in cost. Further objects and advantages-,of 'my invention will appear from the detail description.

In the drawings:

Figure 1 is a diagrammatic view of a neutralizing system embodying my invention;

Figure 2 is a diagrammatic view of a modified form of neutralizing system embodyingfmy invention;

Figure 3 is a diagrammatic view of a second modied form of -neutralizing system embodying my invention;

Figure 4 is a diagrammatic view of a third modified form of neutralizing system embodying my invention;

Figure 5 is a diagrammatic view 'of' a fourth modified form of neutralizing` system embodying my invention;

Figure 6 is a diagrammatic view of a fifth modined form of neutralizing system embodying my invention;

Figure 'l `is a diagrammatic view of a sixth 'modified form of neutralizing system embodying my invention;

Figure 8 is a diagrammatic view of a seventh modified form of neutralizing system embodying my invention;

Figure 9 is a diagrammatic view of an eighth modified form "of neutralizing system embodying my invention;

Figure 10 is a diagrammatic view of a ninth modified form of neutralizing system embodying my invention, in which the transformer means of the power line is electronically coupled to the communication line; and

Figure 11 is a diagrammatic view of a tenth modified form of neutralizing system embodying my invention.

In Figure 1 power line P parallels communication line C, the two lines being spaced a short distance apart as, for example, at opposite sides of a highway. The power line P comprises two wires or conductors I4 and I5 respectively having therein transformers I5 and I1, the latter being a variable transformer. The primaries of transformers I6 and Il are respectively in series with wires I4 and I5, and the secondaries I 6a yand IIa thereof are series connected at one end by a lead I3. Ihe communication line C comprises two signal transmission wires or conductors I9 and 20 respectively having therein variable transformers 2I and 22. The secondaries of the transformers 2l and 22 are respectively in series with the wires I9 and 20, and the primaries 2 Ia and 228v thereof are connected in parallel with each other and respectively in series with secondaries Ia and I'Ilof transformers I6 and I'I, by a lead 23 connecting the adjustable taps of the transformers 2| and 22 together and to the ad- 'ustable tap of secondary Hanf transformer I'I,

and a lead 24 connecting the other end of secondary I6rc1 of transformer I6 to the primaries of transformers 2l and 22.

It will be seen that, in Figure 1, the transformers in the communication line are directly coupled to the transformers in the power line. The transformers I6 and I1 measure the currents flowing in the power line wires I4 and I5, respectively, and the secondaries Il;a and I'Ia of these transformers, being `connected in series, will measure the difference between the two line currents, or the residual current. Accordingly, the current across the transformer secondaries Iiin and 11a will be proportional to the residual curf rent and gives an accurate measure or evalua- -transformers 2| and 22, respectively, and induces in wires I9 and 20 voltage of opposite phase to the interfering voltage induced in the communication line by the power line. In that connection, the phase angle between the primary and secondary of a transformer is extremely small, so that the neutralizing voltage induced in the communication line wires is in reverse phase to the interfering voltage induced in such wires bythe power line, that is, 180 out of phase with the latter voltage, or substantially so. The variable transformers are, of course, properly adjusted to assure that theneutralizing voltage is of sufficient magnitude to assure complete neutralization of the interfering voltage, ample energy being available for that purpose, since the neutralizing energy is; derived directly from the `power yobjectionable condition ordinarily encountered.

It will be understood, however, that this system is equally effective for neutralizing balanced` induction in the communication line, caused by ow of balanced currents in the power line wires. While I preferably provide variable transformers in the power line or in the communication line, or in both, to facilitate proper adjustments to rassure complete neutralization, that is not essential to the broader aspects of my invention, and

Vfixed transformers of proper values may be used ifdesired. Also, if several communication lines bev included in a parallel, each thereof may be neutralized by providing it with transformers similar to transformers 2l and 22, having their primaries connected to leads 23 and 24, extended for that purpose. Further, in cases where a power line and a communication line closely parallel, then separate widely `and again parallel, by overneutralizing the communication line at lone of such parallels to a proper extent it may also be neutralized at the other parallel, avoid- Aing in many cases necessity of duplicate installations of the system of my invention, with a corresponding saving in cost. Since the neutralizing energy is derived directly from the power line, there is available ample energy for overneutraliizing as andfor the purpose stated. Thegeneral system of Figure 1, with slight variations, is applicable to any single or multiphase power line with or without an ungrounded, a unigrounded, or a multigrounded neutral wire, and with or without lightning protection or ground wire; as will appear more fully presently.

In Figure 2 I have shown the neutralizing system of my invention as comprising a power line P1 having three wires or conductors |421, |58L and 25, illustrative of either a three phase, or a three wire single Iphase Edison, power system. The wires I4a and I5a have therein transformers Itb and |'Ib respectively, both variable, and wire 25 has therein a variable transformer 26. The secondaries IBC, I'Ic and 26a of the transformers |6b, I'Ib and 26 are connected' in series, secondary IIc is connected by lead 24a to primaries 2|a and 22a of transformers 2| and 22 in the communication line wires I9 and 20, respectively, as before, and primaries 2| and 22a are connected in parallel with each other and respectively in series with the secondares of the power line transformers. The power line transformers evaluate the interfering effect of that line and, by means of the directly coupled transformers in the communication line, apply to the wires of the latter line voltage of proper phase and magnitude to neutralize completely interfering voltage induced in the communication line by the power line. In referring to complete neutralization of the communication line, I mean that it is complete from a practical standpoint in that any objectionable interference in the communication line by induction from the power line is eliminated, though it may not be theoretically complete. However, if an extremely high degree of neutralization is desired and the power line P1 is a three phase line, the phase angle of the neutralizing voltage may be shifted, by adjusting the turns of the series transformer of the proper phase of the power line, so that the neutralizing voltage is completely in reverse phase to, or 180 out of phase with, the interfering voltage induced in the communication line by the power line. That assures theoretically as was as practically complete neutralization of the communication line.

The system shown in Figure 3 is substantially the same at that of Figure 1, except that the transformer lsb in the power line P2 Wire I4 is variable, and the power line P2 is unigrounded, wire I thereof being grounded at 2T. The transformers in the power line evaluate the disturbing influences in that line arising from steady current flow, stray currents, unbalance due to a fault to ground of one of the power line wires, or other causes, such as would induce interfering voltages in the communication line, and, through their direct coupling to the transformers in the latter line, apply to that line voltages of proper phase and magnitude to effect practically complete neutralization thereof.

Figure 4 shows a neutralizing system embodying my invention applied to a parallel compris ing a unigrounded three phase power line. The arrangement is similar to that of Figure 2, except that the power line P3 includes a fourth wire 28 having therein a xed transformer 29 and groundedl at 30. The secondary 29a of transformer 29 is connected at one end to the ad- `instable tap of the secondary 26a of transformer 26, and the primaries 2 Ia and 229' of transformers 2| and 22 are respectively connected in series with the secondaries of the power line transformers. As before, the transformers in the power line measure or evaluate the interfering with certain exceptions.

effect of that line, and a voltage of proper magnitude and phase angle is introduced into the communication line to neutralize the interfering voltage induced therein by the power line.

Figure 5 shows the neutralizing system of my invention as applied to a parallel including a multigrounded wire for lightning protection. When a multigrounded wire, for example a ground wire for lightning protection, is carried along a power line, a potential is induced and current will flow in that grounded wire. Such current flow will also induce potentials in any nearby communication lines. Since all conductors in a power line are approximately equidistant from the communication line, the induced voltage in the latter line is proportional to the sum of all the currents flowing in the grounded and the ungrounded conductors or wires of the power line. rlhe arrangement of Figure 5 is similar to that of Figure 2, except that a ground wire 3| having multiple grounds 3|, and provided with a variable transformer 32, is included in the power line P4. Secondary 32a of transformer 32 is series connected to secondary llic of transformer IGb and is connected by lead 24b to, primaries 2 |a and 22B of transformers 2| and 22 in wires I9 and 20 of the communication line C. The transformers in the power line evaluate the interfering effect of the power line and apply to the communication line corrective neutralizing voltage of proper phase and magnitude to neutralize the interfering voltage induced in that line by the power line, as before.

The arrangement of Figure 6 is similar to that of Figure 5, except that the wires |4b, I5b and 25a of the power line P5 are not provided with transformers, and ground wire 3| is provided with a fixed transformer 33 the secondary of which is connected, at one end, by lead 24h, to one end of primaries 2|a and 22a of transformers 2| and 22, respectively, the adjustable taps of which are connected by lead 23b to the other end of secondary 33B. Since the ground wire 3| is included in the power line, the energy derivable from that wire is adequate for neutralizing the communication line in the manner above described.

Where the power line potentials are high, the use of series transformers in the conductors or wires of that line would be rather expensive. The use of such transformers may be avoided, with a corresponding saving in expense, by the arrangement shown in Figure '7. That arrangement is similar to the arrangement of Figure 6 No transformer is included in the ground wire 3 Ib, which has multiple grounds 3f, and an auxiliary wire 34, having multiple grounds 34a, is included in the power line PG. The current flowing in auxiliary wire 34 is a measure of the interfering effect of the power line and may be used to induce a neutralizing voltage in the communication line. To that end, auxiliary wire 34 has therein a xed transformer 35 the secondary 35a of which is connected in series with the respective primaries 2| and 22a of the transformers 2| and 22 in wires I9 and 20, respectively, of the communication line C, by leads 23c and 240. The transformer 35 measures or evaluates the interfering effect of the power line and, through its direct coupling to transformers 2l and 22, introduces into the communication line voltage of proper phase and magnitude to neutralize the interfering voltage induced in that line by the power line. The auxiliary wire 34 is much closer to sible. Themethod illustratedinFigurew?? l may y bea-used `with any numberbr arrangement of power Yline wires, including power-lines .with multigrounded neutrals. Ona multigrounded system a Vconsiderable partloftenc40% '110.60 of f'thefphase current Amay `return .in 1the.earth. If there are no grounds withinthe parallel, any one of the system arrangements shown in Eig- -ures 1to'4,.nclusive,.-will operate ,.perfectly. 1i there. are grounds within theparallel, .there .may be more,` .or less, residual --currentl in a. portion of the parallel.otherithany the lportion thereof rwhich isI measuredor-.evaluated `by the neutralizing system, with the `result that lthere r might .be a remnant ofinduction inthe communication line, ifl that were not guarded Aagainst. Such remnant of induction Acan, howevenbe practically entirely eliminated by-proper. adjustment of the number of-turns of ithepower line series transformers.

A'In -cases-lwhere parallels terminate atv either source or loop substations, saving in insu-lation costs rmay be effected by installing the power line series transformersin -the neutral .side of the lphase windings. `In Figure 8, ythe 'parallel terminates at a-source 36-of three phase alternating currentgthegphase windingsv 36%361- and :36 of which 'are fstar connected with ythe 1 neutral point ST-grounde'd lat y31%, and vare Arespectimaly 1 connected -to v-the-wires or conductors-l4c, t|511 and h -of --the power' line P7. 'Transformers 38 aire connected inthe respective phasewi-nfdings Mag-'36h and 36C, with their secondaries-38afseries connectedvand connected .in series -withprimaries 2 Ia and 22e, respectively, lof transformers '-2 I- and 22A inthe communication line wires I9 andf20. The `transformers 38 evaluate the interfering effect Vof vthe power line P7 and, through the direct coupling to the transformers in the lcommunication line, apply tothe latter line voltage of proper iphase and magnitude toneutralize the interfering voltage induced inthe communication line 'by the power line.

The system of `Figure 9 is similar to `that Iof Figure 3, except-that groundy 21 ofjthe llatter vfigure has beenv omitted andl high voltage, protective means Vhas -been provided between the leads 23 and 24. AThe 'high voltage protective means comprises an impedancell yshunted across leads 23 andj24, which are ggrounded lat 4I, and 4 2, respectively, with interveningrspark gaps '43 and 44. This protective means'jfunctionsin a known manner to protect the transformers against injury d ue to" an abrupt great increase in potential on either the :power `line orthe rccmmunication line, due to llightning or other causes, Whilev permitting functioning Y'ofthe system so as'to neutralize interfering voltage induced in the communication-line by `the power line, in the mannerV described with reference 'to Figurey 3. The lhigh voltage ,protective means lshown in Figure 9 is illustrative 'on1y,1and lany other suitableknown protective Imeans may be used, lwithin the broader 4aspects lof f my invention.

l 1InlFigureilO I have vshown a neutralizing system embodying my `invention-in .which 'the series transformers of .thepower line are-electronically coupled to the neturalizing transformer means of thecommunicationline. Thesecondaries 45a, HC and 2lia of theitransformers 45; 'l 1b. ,and 26, in the. wires fl 4d, .fl 5e andy 25, respectively, of the power line` P8. are .connectedin series, as before, it bein'g noted that vthe transformery 45 is fixed and the'transformers Hb Aand/.26am variable, though in each instance the transformer may be either fixedor'variable, as vdesired vor as conditions :may erequire. IThe series .connected secondaries 45, l'lc and .26a-:of thepower line transformers areiconnected at one end, by leadv 24e, tov ground, at "4.1:and ,are connected, attheirfother end, by lead a4(5,Ito the grid circuit aof'an Y.electron tube 48. .The .leads l24e. .andz46 .are'shuntedrby a resistorAGa, andthe gridicircuit of .tube 48.includes the usual grid leak V49. and C.battery v50. The filament .circuitrof tubel 4B includes the usual Avbattery .5I and-the iilamentiis grounded at onefside at 52.

The lplate-'circuit of-tube 48.includes asuitable current source, fsuch'as .the `usual .B battery 53 and, -in series in such circuit, .primarylla of a suitable lcurrent transformera, vwhichmay be an iron core transformer. .',Secondaries55 and v56 of transformer `54 vare variable and .are respectively connected in series with the conductors or wires .19a Iand 20a of the communicationline C1. Theinterferingzeiect ofthe powerline P5 is measuredby'th'e seriestransformers therein. The :voltage drop .acrossresistorMi, produced by flow ofthe dilferentialcurrentas measured by the power linetransf ormers, .is impressed. onthe grid cof 1tube-48, 'causing corresponding but greater changes in 'the plate .current iiowing through primary 514a of transformer 54. "That inducescorresponding voltage in' the secondariesr55 and 56, thereby applying to communication line wires 119e- .and A2lia .voltage of rproper` phase and magnitude-to neutralize the interferingvoltage induced in those wires by the power line. Electronic couplingA between the .series transformers of the powerd-ine -and the :neutralizing .transformer meanswof the'ccmmunication. line, suchas shown lin-ligure 101has certain ,advantages Vover :electromagnetic coupling. -In electronic coupling ithe degree vof. neutralization is lreadily variable to follow the'fslight seasonal lchanges innearth resistivityfor to allow for changes in-the'length of a parallelf'due lto switching. `'If desired, in the system of Figure 10, resistance coupling may be used instead of electronic coupling.

f The system of Figure 11 is similar to that of Figure 5,eXcept thatthe secondaries lof the power line series current transformers are-connected in shunt across 'the leads 24I and 23d, instead -of being connected in series Ias--in Figure 5. Under conditions of unbalance Aof the power line such as lare ordinarily encountered, connecting the secondaries Iof the power-line transformers in series gives entirely satisfactory results with respect to neutralizing the interfering vvoltages inducedinthe communication line by the power line, and probably would be satisfactory even in cases of exceptionally great unbalance of the powerV line.v However, by'connecting'the secondaries of4 the power line transformers in shunt, I render available more energy for neutralizing thecommunication line, in the case of exceptionallygreat-unbalance of the power line, than would be available were` such secondaries connected in series.' thereby assuring complete neutralizing 'of the communication line even under such exceptional conditions. In either casewhether the power line secondaries be connected in series or in shuntthe power line transformers evaluate the interfering eiect, or current differential, of the power line with respect to the communication line and provide adequate energy for neutralizing the communication line, in the manner above explained. From what has been said, it will be understood that, if desired, in the systems of Figures 1 to 5, inclusive, the secondaries of the power line transformers may be connected in shunt instead of in series and, in either case, will function as and for the purpose previously described. Likewise, in the systems of Figures 8 to 10, inclusive, the secondaries of the power line transformers may be connected in shunt.

In general only one neutralizing system will be required for each parallel. Where the parallel is of considerable length, or the power line or the communication line is sectionalized or has taps taken olf, or where it appears advisable for other reasons, a plurality of neutralizing systems may be included in a parallel. In such case, each system is adjusted to neutralize that portion of the total interfering induction which is likely to arise from the corresponding area of the parallel.

In order to facilitate illustration and description of the neturalizing system of my invention, I have shown it as used with a communication line spaced an appreciable distance from the power line. That is not essential, however, and it may be used on communication lines carried on either the same poles or cable runs as the power line, or on different poles or cable runs. izing system of my invention is completely automatic, requires no attendance and but little maintenance, and is automatically taken out of service with the power line, unless that line is grounded,

in which case it remains effective for neutralizing i While it is, in general, simpler to evaluate the interfering effect of the power line by series current transformers, with but two leads connecting them to the communication line transformers, as shown, the system of my invention comprehends connecting each of the series transformers in the power line wires, by separate leads, to the transformers in the communication line, and there evaluating the interfering eifect of the power line and applying to the communication line wires voltage of proper phase and magnitude to neutralize the interfering voltage induced by the power line.

I have shown, for simplicity of illustration, a single communication line comprising but two conductors or wires. It will be understood, however, that the neutralizing system of my invention is equally applicable to neutralizing the induced voltages on communication circuits c1' leads-a plurality of circuits-comprising any number of conductors or wires. In such cases, each installation of series transformers in the power line may be connected by leads to the corresponding transformers in the different classes or routes of communication circuits regardless of their position or separation with respect to the power line, the transformers in the power line, or in the communication line, or in both, being, of course, properly adjusted to eifect the desired neutralizing of the interfering voltage induced in the communicaticn line by the power line. Also, if a The neutralroute include two or more power lines paralleling a communication line or lead, the series transformers in each of the power lines may be connected to the transformers of the communication line or lead for neutralizing the interfering voltage induced therein by the power lines, in the manner above described. It is possible, by the system of my invention, to evaluate the interfering effect of all power lines along a route regardless of the number of such lines, the number of phases in each line, and the voltages of the various power lines, and to apply neutralizing voltage to a communication line or lead included in a parallel of such route, as will be understood from the preceding description of such system.

As has been indicated, and as Will be understood by those skilled in the art, changes in detail may be made in my invention, both as to the system and as to the method, without departing from the eld and scope thereof, and I intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred forms only of my invention have been disclosed.

I claim:

1. In a neutralizing system comprising a power line and a communication line having portions thereof in adjacent parallel relation, each of said lines comprising a plurality of wires, current transformers having their primaries respectively in series with the power line wires and their secondaries connected in series, neutralizing transformers having their secondaries respectively in series with the communication line wires and their primaries connected in shunt, and means metallically connecting the primaries of said neutralizing transformers respectively in series with the secondaries of said power line transformers.

2. In a neutralizing system comprising a power line and a communication line having portions thereof in adjacent parallel relation, the power line comprising a plurality of transmission wires and a ground wire in the parallel thereof and the communication line comprising a plurality of transmission wires, current transformers having their primaries respectively in series with the power line transmission and ground wires and their secondaries connected in series, neutralizing transformers having their secondaries respectively in series with the communication line wires andtheir primaries connected in shunt, and means metallically connecting the primaries of said neutralizing transformers respectively in series with the secondaries of said power line transformers.

3. In a neutralizing system comprising a power line and a communication line having portions thereof in adjacent parallel relation, the power line comprising a plurality of transmission wires and a ground wire in the parallel thereof and the communication line comprising a plurality of transmission wires, a current transformer having its primary in series with said ground wire, neutralizing transformers having their secondaries respectively in series with the communication line wires and their primaries connected in shunt, and means metallically connecting the primaries oi said neutralizing transformers respectively in series with the secondary of said ground wire transformer.

4. In a neutralizing system comprising a power line and a commmunication line having portions thereof in adjacent parallel relation, each of said lines comprising a plurality of wires, current arcane# transformers having their' secondaries )series con# ne'cted and 'theirprm'aries respectively'connect-ed in series'with thepovverT line wires., neutralizing' transformer' means havingV 'secondaries fres'pe'c tively connected in "series withthej communication line wires; and 'means' electronically' coupling the secondaries of the power line transformers to the' primary of saidv neutralizingtransformer means. I t A In aneutralizing Isystem comprising; a powerv lineand a communication line havingportio'ns thereofl inadjacient'par'allel relation, each of 'said' lines"comprising a lplurality ofv wires', current transformers having their secondaries seriescon4 necte'd and their primaries respectively connected' iriser'i'es with'the power line wires,A an'electron tube having grid, filament and plate "circuit's; ay neutralizing transformer having' aV primaryin` series in the plate circuit of'said tube andfse'c-v onda'ries respectively'connected in' series with thev communication line' wires, leads respectively connecting one end of the* secondariesofthe power; line' transformers to groundan'd the Aother end thereof to the grid voi?""saidtube', and-aresistor shunted across said leads.

6. In'a neutralizing system comprising'apower lineand acommunicationliner having portions thereof inadjacent'parallel relation', each of'said lines "comprising a plurality'of` wires; current transformers having their primariesl respectively connected in series withthe' power line wires and theirlsecondaries `connected in shunt, andneu tralizing transformers having f' theii` secondariesrespectively in seri'es 'with the communication line' wires and their primaries connected'inshun't with each other' and? respectively "in shuntwltn the secondaries of saidl power line.' transformers;

7.' In a-neutralizing'system comprisinga `povver line and a communication line having portions' thereofin adjacent Sparallel' relation; the? power line'- comprising' a plurality of transmission wirres and a" ground wire in the parallel thereof' andthe' communication line comprising a' plurality V of transmission' wires, current transformers having their primaries "respectively-in series l`with` the power line transmission'and groundwire's vand their secondaries' vconnected' in shunt, and lneu'- tr'alizingl transformers having" their" secondaries respectively in series with' thecommunication line wires'and their primaries connected in -sli'unt with each other and' respectively in shuntwith the' secondaries of said powerline transformers.

8g' Means for neutralizing fthevoltage inducedbyfa power'line' in `a parallel communication line formedbyl a pair of conductors comprising, in combination, secondary winding 'l means inductivelyfrelated' tosaid'power line for induction therein'ofa'voltage which is a function of said indcdvol't-age; a primary` windingv individual to'fand'inductively related to each of' said `conductors vof vsaid communication line, and means couplingsaid secondary winding means to each ofsaidprimaryf'windings whereby a voltage is induced? inv sa'id communication line to neutralize said induced'voltage.

9.: Means: for neutralizing-the voltage induced by fa' power line in" afparallel communication line formedby a'A pair of conductors comprising, in combination, secondaryV winding means inductively'l related to'said power line for induction therei'niofavoltage whichis a function of said inducedfvoltage, ar primary Winding individual to'andfinductivelyrelated' to each of said conductorsofsaid communication line, and conducto'i" means interconnectingsaid secondary winding 'means tojleach of said primary windings Wher'ehy'a voltage induced in said communicationline to neutralize vsaid induced voltage.

101 :Means for" neutralizing vthe-voltage 'induced byapower'linein'a parallel communication line frrr'ic'i"byf'aV` pairtofA conductors comprising, in cmination,"secondary winding means inductively'related to y'saiddp'oviier'line for induction therein oif afvoltage which? is a function of said induced-voltage; a'pri'ma-ry winding .individual tofandfinduct'ively vrelated/*to` each" of said condiitrs Aof said vcOrrinuinication line, l means coupling;sa-idfisecondary"winding means to each of said prima-ry "windings` whereby a voltage is in duced C"in" said f cm'rruncation' linel to neutralize saidinduced voltage, andme'ans for adjusting the effu tive nuinher'bf' turns of Ieach oi said pri-mary windings:

HOLLAEDWIN' WEA-VER'.

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